I would go to the Library and probably read. I would check out one or two books that looked good (possibly on Equestrian history) and read them while I walked around Ponyville, chatting to anypony I ran into that I knew, and trying to avoid detection by the Party Squad (consisting of Pinkie Pie), since I don't really like attention, and as soon as Pinkie saw me, she would want to throw a party. Not that I don't like Pinkie; I just don't like parties. Of course, if she did throw a party, I would go so as to not hurt her feelings, but I'd probably just hide in a corner and read. I would love to find out about how magic works, since I would be a unicorn of course, and I would certainly try to find a way to be able to stay!
Find a way to stay there forever Then I would start a band and sing all of the hit songs from earth and claim that I made them. As a result I will be a trillionare and then overthrow celestia's spot as ruler of the world. Either that, or go gardening :3
Call me simple, but I wouldn't do all that much. I'm there for a day, so in that given time I would definitely take part in any sort of event that may be in the works. Other than that, I'd probably just sit around in the middle of the town on a bench and enjoy the day and the people around me. I'm given a day in a perfectly peaceful world, so why not just enjoy the peace I'm given? If it's a spell or some silly shenanigans keeping me there though, I suppose I would take a few hours researching something about it, and if the opportunity or chance arises to break free of it and stay permanently, then that would be the obvious choice, but otherwise as said before, I'd just sit there and crash on a bench, soak up the sunshine, grab a snack, and enjoy the hospitality of the populace.
Adding to my evil plot idea. Couldn't you just cause havoc? Or even do something so big that it'll alter the real show back on earth? I mean, you're only staying for a day, it's not like they'll catch you. I'm not saying that I'll do that.... :/
Find a way to stay, make friends, be happy, blend in (Somehow) and occasionaly find a way to troll the show.
I'd probably go hang out with Fluttershy. That or find Twilight and see about a way to bring me back whenever I wanted.
I'd read a few hundred books in ten minutes flat, followed by hanging out with Fluttershy and Rainbow Dash for a couple of hour, maybe racing Dash (and losing). Then, I'd spend some time getting to know Luna, maybe ask her why she didn't attend the GGG. Follow that up with a dinner with the mane six. Just before leaving, I'd see what Poison Joke can do to me. Above all else: NO PARTIES! Too much social activity for me... BTW, in this, I'm a Pegasus stallion.
I've put more thought into this. If I go and become a pony for 24 hours. I'd just chill in ponyville. If I go and I'm human. That could be interesting. Even better if I kept all my stuff on me at the time I go. First I'd turn on Iamsleepless and just chill in ponyville. Like the town square. I'm not sure how ponies would react to a 6 foot tall human wearing all black clothes. They might be scared to come up to me. They might see me as a threat. Which would probably get Celestia and the mane 6 to show up and question me. Depending how that goes, it decides what happens. Maybe the mane 6 invite me on a tour of ponyville. I'd gladly go. I'd spend whatever time left just hanging with them. If they don't offer to hang out, I'd go back to just hanging around ponyville. Maybe go to sugar cube corner and get some food. If any pony would come up to me I'd share my music, ask about their life and just talk to them. Assuming I befriend one pony at all. I'd give them a keychain. I have 4 of them on my key ring. Not sure what a pony could give me, but whatever they give, if anything at all. I'd tresure it. Then when my time is up, I'd hope that when I return all my memories of it stay and whatever I had on me returns with me. -- Sent from my Palm Pre using Forums
I imagine the whole time would be spent in Twilight's library, browsing her literature and swapping knowledge from our respective worlds.
I would Find a way to stay there then go on adventures with the mane six and hang out, and occasionally see and talk to my sisters (Luna and Celestia.)
Most likely love to learn history and learn how to learn how to sew from rarity and well go hang out with Luna or Princess Cadence c: and meet Rainbow dash and the rest of the Mane 6 and Tell Derpy and everyone about the fandom xD
Sorry new don't know how to post answers, but i would spend my day with twilight or Celestia and have them cast a spell to let me stay forever.
I'D THROW A PARTY AT TWILIGHT'S HOUSE FOR ALL OF PONYVILLE!! :'D so i could read some of her books and meet everyone :'D and at the end of the night i'd take a walk with fluttershy into the forest...we share a romantic evening and i ask her to marry me and then i wake up -.e; *sigh* ,-,
I would go to Lyra's and hang with her revealing anything she wishes to know about humans then go to Celestia ask if I could stay forever and help improve equestria's tech level.
I'd spend it with my two favorite ponies, Dashie and AJ. As far as what I would do, I don't really know so I would play it by ear.
If I could go to Ponyville, I would go and visit Applejack at her farm and get a lot of apples and learn about farm life. Then party with Pinkie, and become friends with the ponies. Then hang out with Fluttershy and see all her animal friends. Then save the best for last and learn how to be a cool, kick-flank flying Pegasus from the Dr. Dash. Any other time I would have is to go and read with Twilight, not caring much to hang out with Rarity.